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//! [0]
    class MyGLWindow : public QWindow, protected QOpenGLFunctions
    {
        Q_OBJECT
    public:
        explicit MyGLWindow(QScreen *screen = nullptr);

    protected:
        void initializeGL();
        void paintGL();

        QOpenGLContext *m_context;
    };

    MyGLWindow(QScreen *screen)
      : QWindow(screen), QOpenGLWidget(parent)
    {
        setSurfaceType(OpenGLSurface);
        create();

        // Create an OpenGL context
        m_context = new QOpenGLContext;
        m_context->create();

        // Setup scene and render it
        initializeGL();
        paintGL();
    }

    void MyGLWindow::initializeGL()
    {
        m_context->makeCurrent(this);
        initializeOpenGLFunctions();
    }
//! [0]

//! [1]
    void MyGLWindow::paintGL()
    {
        m_context->makeCurrent(this);
        glActiveTexture(GL_TEXTURE1);
        glBindTexture(GL_TEXTURE_2D, textureId);
        ...
        m_context->swapBuffers(this);
        m_context->doneCurrent();
    }
//! [1]

//! [2]
    QOpenGLFunctions glFuncs(QOpenGLContext::currentContext());
    glFuncs.glActiveTexture(GL_TEXTURE1);
//! [2]

//! [3]
    QOpenGLFunctions *glFuncs = QOpenGLContext::currentContext()->functions();
    glFuncs->glActiveTexture(GL_TEXTURE1);
//! [3]

//! [4]
    QOpenGLFunctions funcs(QOpenGLContext::currentContext());
    bool npot = funcs.hasOpenGLFeature(QOpenGLFunctions::NPOTTextures);
//! [4]
